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From the Institute of Pharmacology,*
University of
Messina, Messina, Italy; the William Harvey Research
Institute,
St. Bartholomews, and the Royal
London School of Medicine and Dentistry, Charterhouse Square, London,
United Kingdom; and the Department of
Biomorphology,
School of Medicine, the
Department of Veterinary Medicine and
Pharmacology,§
and the Institute of Veterinary
General Pathology and Pathological Anatomy,
University of Messina, Messina, Italy
| Abstract |
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| Introduction |
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(TNF
), interleukin IL)-1,
IL-6,or IL-8], the expression on endothelium and neutrophils of
adhesion molecules (eg, VCAM-1, ICAM-1), and the overproduction
of vasoactive mediators [eg, nitric oxide (NO) by inducible NO
synthase (iNOS) or eicosanoids by cyclooxygenase-2 (COX-2)] play
important roles in the pathophysiology of inflammation. The expression
of inducible genes leading to the formation of these proteins relies on
transcription factors, which are controlled by (other) inducible genes
and, hence, require de novo protein synthesis or
alternatively by so-called primary transcription factors. Among the
latter, nuclear factor
B (NF-
B) has received a considerable
amount of attention because of its unique mechanism of activation and
its active role in cytoplasmic/nuclear signaling, and its rapid
response to pathogenic stimulation of NF-
B plays a central role in
the regulation of many genes responsible for the generation of
mediators or proteins in inflammation. These include the genes for
TNF
, IL-1, IL-6, IL-8, VCAM-1, ICAM-1, iNOS, and COX-2, to name but
a few.1,2
The discovery in 1997 that inhibition of the
activation of NF-
B may be useful in conditions associated with local
or systemic inflammation3
stimulated the search for agents
that prevent the activation of NF-
B.
There is evidence that inhibition of the
activation of the neutral protease calpain prevents the activation of
NF-
B. Calpain is one of the many intracellular proteins, the
activity of which is dependent on intracellular calcium levels. To
date, two isoforms of calpain have been identified: calpain I (or
µ-calpain) and calpain II (or m-calpain), which require,
respectively, low and high micromolar concentrations of calcium for
their activation.3,4
After activation by calcium, calpain
cleaves a specific subset of cellular proteins. For instance,
activation of calpain I leads to the degradation of I
B (I
B
or
I
Bß) in the proteasome and, hence, is an essential step in the
translocation of NF-
B from the cytosol into the
nucleus.5,6
This calpain-dependent step of the activation
of NF-
B is abolished by calpain inhibitor I.7-10
Thus,
calpain inhibitor I prevents the expression of many NF-
B-dependent
genes, including those for iNOS11-13
and
COX-2.14,15
In addition to proteins regulated by NF-
B,
the generation of superoxide anions, hydroxyl radicals, and
peroxynitrite also plays a pivotal role in the tissue injury associated
with inflammation.16-20
Hydroxyl radicals can cause DNA
damage,21,22
resulting in the activation of the nuclear
enzyme poly(ADP-ribose) synthetase (PARS), depletion of NAD and ATP,
and ultimately cell death.23
This study investigates the effects of calpain inhibitor I in animal models of acute (carrageenan-induced pleurisy) and chronic (collagen-induced arthritis) inflammation in the rat. In particular, we investigate the effects of calpain inhibitor I on the lung injury associated with carrageenan-induced pleurisy and the joint injury associated with collagen-induced arthritis. To gain a better insight into the mechanism(s) of action of calpain inhibitor I, we have also investigated the effects of calpain inhibitor I on the expression of iNOS and COX-2, the nitration of cellular proteins by peroxynitrite, and the activation of the nuclear enzyme PARS.
| Materials and Methods |
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Male Sprague-Dawley and Lewis rats (160180 g; Charles River, Milan, Italy) were housed in a controlled environment and provided with standard rodent chow and water. Animal care was in compliance with Italian regulations on the protection of animals used for experimental and other scientific purposes (D.M. 116192) as well as with EEC regulations (O.J. of E.C. L 358/1 12/18/1986).
Experimental Groups (Pleurisy Study)
In the treated group of animals, calpain inhibitor I was given as an intraperitoneal (i.p.) bolus 15 minutes before carrageenan (520 mg/kg) (CAR + Calp-I group). In a vehicle-treated group of rats, vehicle (the final concentration of ethanol was 1%) was given instead of calpain inhibitor I (CAR group). In separate groups of rats, surgery was performed that was identical in every aspect to the surgery performed on the CAR group, except that saline was injected instead of carrageenan (sham group; Sham). In an additional group of animals, sham surgery was combined with the administration of calpain inhibitor I (520 mg/kg) (Sham + Calp-I).
Carrageenan-Induced Pleurisy
Rats were anesthetized with isoflurane, and a skin incision was
made at the level of the left sixth intercostal space. The underlying
muscle was dissected, and saline (0.2 ml) or saline containing 1%
-carrageenan (0.2 ml) was injected into the pleural cavity. The skin
incision was closed with a suture, and the animals were allowed to
recover. At 4 hours after the injection of carrageenan, the animals
were killed by inhalation of CO2. The chest was
carefully opened, and the pleural cavity was rinsed with 2 ml of saline
solution containing heparin (5 U·ml-1) and
indomethacin (10 µg·ml-1). The exudate and
washing solution were removed by aspiration, and the total volume was
measured. Any exudate that was contaminated with blood was discarded.
The amount of exudate was calculated by subtracting the volume injected
(2 ml) from the total volume recovered. The leukocytes in the exudate
were suspended in phosphate-buffered saline (PBS) and counted with an
optical microscope in a Burkers chamber after vital Trypan Blue
staining.
Measurement of Nitrite/Nitrate
Nitrite + nitrate production, an indicator of NO synthesis, was measured in the supernatant samples as previously described.18 Briefly, the nitrate in the supernatant was first reduced to nitrite by incubation with nitrate reductase (670 mU·ml-1) and NADPH (160 µmol/L) at room temperature for 3 hours. The nitrite concentration in the samples was then measured by the Griess reaction, by adding 100 µl of Griess reagent (0.1% naphthylethylendiamide dihydrochloride in H2O and 1% sulfanilamide in 5% concentrated H3PO4; 1:1, v/v) to 100-µl samples. The optical density at 550 nm (OD550) was measured using an enzyme-linked immunosorbent assay microplate reader (SLT- Labinstruments, Salzburg, Austria). Nitrate concentrations were calculated by comparison with OD550 of standard solutions of Dulbeccos minimum essential medium.
Leukocyte Count
Blood samples (taken from the femoral vein) for a peripheral cell count were taken 4 hours after the administration of carrageenan. The total number of peripheral leukocytes is expressed as white blood cell count (WBC) per µl (mean ± SEM).
Induction of Collagen-Induced Arthritis
Bovine type II collagen (CII) was dissolved in 0.01 mol/L acetic acid at a concentration of 2 mg/ml by stirring overnight at 4°C. Dissolved CII was frozen at -70°C until use. Complete Freunds adjuvant (CFA) was prepared by the addition of Mycobacterium tuberculosis H37Ra at a concentration of 2 mg/ml. Before injection, CII was emulsified with an equal volume of CFA. Collagen-induced arthritis was induced as previously described.24 On day 1, Lewis rats were injected intradermally at the base of the tail with 100 µl of the emulsion (containing 100 µg of CII). On day 21, a second injection of CII in CFA was administered. In a separate set of experiments, animals were treated with calpain inhibitor I (n = 10) (5 or 2.5 mg/kg, i.p.) every 48 hours, starting from day 24.
Clinical Assessment of CIA
Rats were evaluated daily for arthritis by using a macroscopic scoring system: 0 = no signs of arthritis, 1 = swelling and/or redness of the paw or one digit, 2 = two joints involved, 3 = more than two joints involved, and 4 = severe arthritis of the entire paw and digits.24 The arthritic index for each rat was calculated by adding the four scores of individual paws. Clinical severity was also determined by quantitating the change in the paw volume, using plethysmometry (model 7140; Ugo Basile).
Assessment of Arthritis Damage
At day 35, animals were sacrificed while they were under anesthesia, and paws and knees were removed and fixed for histological examination, which was done by an investigator blinded for the treatment regime. The following morphological criteria were considered: score 0, no damage; score 1, edema; score 2, inflammatory cell presence; score 3, bone resorption.
Histological Examination
Lung biopsies were obtained 4 hours after injection of carrageenan, and paws and knees, 35 days after CIA. The biopsies were fixed for 1 week in buffered formaldehyde solution (10% in phosphate-buffered saline) at room temperature, dehydrated by graded ethanol, and embedded in Paraplast (Sherwood Medical, Mahwah, NJ). The paws were trimmed, placed in decalcifying solution for 24 hours, embedded in paraffin, and sectioned at 5 g. Tissue sections were deparaffinized with xylene, stained with trichromic Van Gieson, and studied using light microscopy (Dialux 22 Leitz).
Radiography
The rats were anesthetized with sodium pentobarbital (45 mg/kg, i.p.). Rats were placed on a radiographic box 90 cm from the X-ray source. Radiographic analysis of normal and arthritic rat hind paws was performed by X-ray machine (Philips X12, Germany) with a 40-kW exposition for 0.01 seconds. An investigator blinded for the treatment regime determined the radiograph score. The following radiograph criteria were considered: score 0, no bone damage; score 1, tissue swelling and edema; score 2, joint erosion; score 3, bone erosion and osteophyte formation.
Immunohistochemical Localization of Nitrotyrosine
Tyrosine nitration, an index of the nitrosylation of proteins by peroxynitrite and/or oxygen-derived free radicals, was determined by immunohistochemistry as previously described.18 At the end of the experiment, the relevant organs were fixed in 10% buffered formaldehyde, and 8-µm sections were prepared from paraffin-embedded tissues. After deparaffinization, endogenous peroxidase was quenched with 0.3% H2O2 in 60% methanol for 30 minutes. The sections were permeabilized with 0.1% Triton X-100 in PBS for 20 minutes. Nonspecific adsorption was minimized by incubating the section in 2% normal goat serum in PBS for 20 minutes. Endogenous biotin- or avidin-binding sites were blocked by sequential incubation for 15 minutes with avidin and biotin. The sections were then incubated overnight with a 1:1000 dilution of primary anti-nitrotyrosine antibody or with control solutions. Controls included buffer alone or nonspecific purified rabbit IgG. Specific labeling was detected with a biotin-conjugated goat anti-rabbit IgG and avidin-biotin peroxidase complex.
Immunohistochemical Localization of PARP
At the specified time after the carrageenan injection, lung tissues were fixed in 10% buffered formalin, and 8-µm sections were prepared from paraffin-embedded tissues. After deparaffinization, endogenous peroxidase was quenched with 0.3% H2O2 in 60% methanol for 30 minutes. The sections were permeabilized with 0.1% Triton X-100 in PBS for 20 minutes. Nonspecific adsorption was minimized by incubating the section in 2% normal goat serum in PBS for 20 minutes. Endogenous biotin- or avidin-binding sites were blocked by sequential incubation for 15 minutes with avidin and biotin (DBA, Milan, Italy). The sections were then incubated overnight with a 1:500 dilution of primary anti-poly(ADP-ribose) antibody (DBA) or with control solutions. Controls included buffer alone or nonspecific purified rabbit IgG. Specific labeling was detected with a biotin-conjugated goat anti-rabbit IgG and avidin-biotin peroxidase (DBA).
Myeloperoxidase Activity
Myeloperoxidase (MPO) activity, an indicator of polymorphonuclear leukocyte (PMN) accumulation, was determined as previously described.25 At the specified time after the intrapleural injection of carrageenan, lung tissues were obtained and weighed. Each piece of tissue was homogenized in a solution containing 0.5% hexadecyltrimethylammonium bromide dissolved in 10 mmol/L potassium phosphate buffer (pH 7) and centrifuged for 30 minutes at 20,000 x g at 4°C. An aliquot of the supernatant was then allowed to react with a solution of tetramethylbenzidine (1.6 mmol/L) and 0.1 mmol/L H2O2. The rate of change in absorbance was measured spectrophotometrically at 650 nm. MPO activity was defined as the quantity of enzyme degrading 1 µmol of peroxide/min at 37°C and was expressed in milliunits per gram weight of wet tissue.
Malondialdehyde Measurement
Malondialdehyde (MDA) levels in the lung tissue were determined as an indicator of lipid peroxidation.26 Lung tissues, collected at the specified time, were homogenized in 1.15% KCl solution. An aliquot (100 µl) of the homogenate was added to a reaction mixture containing 200 µl of 8.1% sodium dodecyl sulfate, 1500 µl of 20% acetic acid (pH 3.5), 1500 µl of 0.8% thiobarbituric acid, and 700 µl of distilled water. Samples were then boiled for 1 hour at 95°C and centrifuged at 3000 x g for 10 minutes. The absorbance of the supernatant was measured by spectrophotometry at 650 nm.
Determination of Nitric Oxide Synthase Activity
The calcium-independent conversion of L-arginine to L-citrulline in the homogenates of either pleural macrophages or lungs (obtained 4 hours after carrageenan treatment in the presence or the absence of calpain inhibitor I) served as an indicator of iNOS activity.27 Cells were scraped into a homogenation buffer composed of 50 mmol/L Tris-HCl, 0.1 mmol/L EDTA, and 1 mmol/L phenylmethylsulfonyl fluoride (pH 7.4) and homogenized in the buffer on ice, using a tissue homogenizer. Conversion of [3H]L-arginine to [3H]L-citrulline was measured in the homogenates as described.28 Briefly, homogenates (30 µl) were incubated in the presence of [3H]L-arginine (10 µmol/L, 5 kBq per tube), NADPH (1 mmol/L), calmodulin (30 nmol/L), tetrahydrobiopterin (5 µmol/L), and EGTA (2 mmol/L) for 20 minutes at 22°C. Reactions were stopped by dilution with 0.5 ml of ice-cold HEPES buffer (pH 5.5) containing EGTA (2 mmol/L) and EDTA (2 mmol/L). Reaction mixtures were applied to Dowex 50W (Na+ form) columns, and the eluted [3H]L-citrulline activity was measured with a Beckman scintillation counter.
Measurement of Prostaglandin E2 in the Pleural Exudate
The amount of prostaglandin E2 (PGE2) present in the pleural fluid was measured by radioimmunoassay without prior extraction or purification.29
Assessment of COX Activity
Lungs were obtained 4 hours after the induction of pleurisy by
carrageenan injection. The material was homogenized at
4°C in a buffer containing protease inhibitors in a ratio of
5:1 (v/w). The protein concentration in the homogenates was measured by
the Bradford assay,30
with bovine serum albumin used as
standard. Homogenates were incubated at 37°C for 30 minutes in the
presence of excess arachidonic acid (30 µmol/L). The samples were
boiled and centrifuged at 10,000 x g for
minutes. The concentration of
6-keto-PGF1
present in the supernatant was
measured by radioimmunoassay as previously described.31
Immunohistochemical Localization of COX-1 and COX-2
Lung biopsies were fixed in 10% buffered formalin, and 8-µm sections were prepared from paraffin-embedded tissues. After deparaffinization, endogenous peroxidase was quenched with 0.3% H2O2 in 60% methanol for 30 minutes. The sections were permeabilized with 0.1% Triton X-100 in PBS for 20 minutes. Nonspecific binding was minimized by incubating the section in 2% normal goat serum in PBS for 20 minutes. Endogenous biotin- or avidin-binding sites were blocked by sequential incubation for 15 minutes with avidin and biotin (DBA). The sections were then incubated overnight with a 1:500 dilution of the primary anti-COX-1 or anti-COX-2 antibody with (DBA) or with control solutions. Controls included buffer alone or nonspecific, purified rabbit IgG. Specific labeling was detected with a biotin-conjugated goat anti-rabbit IgG and avidin-biotin peroxidase (DBA).
Materials
Unless otherwise stated, all compounds were obtained from
Sigma-Aldrich Company (Poole, Dorset, UK). Thiopentone sodium (Intraval
Sodium) was obtained from Rhône Mérieux (Harlow, Essex,
UK). Biotin blocking kit, biotin-conjugated goat anti-rabbit IgG,
primary anti-nitrotyrosine, anti-poly(ADP-ribose) synthetase
antibodies, primary anti-iNOS, anti-COX-2, and avidin-biotin peroxidase
complex were obtained from DBA. Calpain inhibitor 1 (Cal I-1) was
purchased from Calbiochem Novabiochem (Nottingham, UK). Antibodies to
I
B
and I
Bß were purchased from Santa Cruz
Biotechnology (USA). All other chemicals were of the highest commercial
grade available. All stock solutions were prepared in nonpyrogenic
saline (0.9% NaCl; Baxter Health Care, Thetford, UK).
Statistical Evaluation
All values in the figures and text are expressed as mean ± SEM of n observations. For the in vivo studies n represents the number of animals studied. In the experiments involving histology or immunohistochemistry, the figures shown are representative of at least three experiments performed on different experimental days. Data sets were examined by one- or two-way analysis of variance, and individual group means were then compared with Students unpaired t-test. For the arthritis studies, a Mann-Whitney U test (two-tailed, independent) was used to compare medians of the arthritic indices.32 A P value less than 0.05 was considered significant.
| Results |
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All rats that were treated with carrageenan developed an acute
pleurisy, characterized by the production of turbid exudate (Table 1)
. When compared with the number of
cells collected from the pleural space of sham-operated rats (Table 1)
,
injection of carrageenan induced a significant increase in the number
of PMNs (Table 1)
. Pretreatment of rats with calpain inhibitor I
attenuated the volume of the pleural exudate as well as the number of
PMNs within the exudate in a dose-related fashion (Table 1)
.
Carrageenan administration also led to a significant increase in the
number of circulating leukocytes (WBC count, Table 2
). This increase in WBC count caused by
administration of carrageenan was not affected by treatment of rats
with calpain inhibitor I (Table 2)
.
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was significantly increased in
comparison with sham rats (Table 1)
was significantly reduced in the
lungs from carrageenan-treated rats that had been pretreated with
calpain inhibitor I (Table 1)COX-1 was also detected by immunohistochemical analysis in the lung sections obtained from rats treated with carrageenan, but the degree of staining was similar to that observed in the lungs of sham-operated control animals (data not shown). The degree of staining for COX-1 in lungs of carrageenan-treated rats treated with calpain inhibitor I was similar to that observed in lungs obtained either from carrageenan-treated rats or from sham-operated rats (data not shown).
All rats that were treated with carrageenan exhibited a substantial
increase in the activities of MPO and MDA in the lungs (Figure 3, A and B)
. Pretreatment of rats with
calpain inhibitor I attenuated the increase in MPO and MDA caused by
carrageenan in the lung (Figure 3, A and B)
. In sham-operated rats,
calpain inhibitor I had no effect on any of the parameters measured
(Figure 3, A and B)
. Histological examination of lung sections of rats
treated with carrageenan showed edema, tissue injury, and infiltration
of the tissue with PMNs, lymphocytes, and plasma cells (Figure 4A)
. Calpain inhibitor I treatment
reduced both lung injury as well as infiltration of the tissue with
white blood cells (Figure 4B)
.
|
|
CIA developed rapidly in rats immunized with CII, and clinical
signs (periarticular erythema and edema) of the disease (Figure 5A)
first appeared in the hind paws
between 24 and 26 days postchallenge. Furthermore, a 100% incidence of
CIA was observed by day 27 in CII-immunized rats. Neither the clinical
signs nor the histopathological features of CIA were observed in rat
forepaws during the 28-day evaluation period. The maximum incidence of
CIA in the calpain inhibitor I-treated rats during the 35-day study
period was 55% (Figure 5A)
(P < 0.05).
|
The data in Figure 5D
demonstrate a time-dependent increase in hindpaw
(each value represents the mean values of both hind paws) volume (ml)
in rats immunized with CII. Maximum paw volume occurred by day 28 in
the CII-immunized rats. Calpain inhibitor I significantly suppressed
hindpaw swelling from day 24 to day 35 postimmunization in a
dose-dependent fashion (Figure 5D)
. A maximum reduction in response
hindpaw swelling of 66% was observed from day 28 to day 35. No
increase in hindpaw volume over time was observed in normal rats
(Figure 5D)
.
The rate and the absolute gain in body weight were comparable in normal
Lewis rats and CII-immunized rats for the first week (Figure 5C)
.
Beginning on day 25, the collagen-challenged rats gained significantly
less weight than the normal rats, and this trend continued through day
35. Calpain inhibitor I attenuated (in a dose-dependent fashion) the
weight loss caused by immunization with CII (when compared with the
respective control group).
The histological evaluation (at day 35) of the paws in the
vehicle-treated arthritic animals revealed signs of severe arthritis,
with massive infiltration of the tissue with white blood cells
(neutrophils, macrophages, and lymphocytes). In addition, severe or
moderate necrosis and sloughing of the synovium were seen, together
with the extension of the inflammation into the adjacent musculature,
with fibrosis and increased mucous production (Figure 6A
; see Figure 7A
for the damage score). In the calpain
inhibitor I-treated animals, the degree of arthritis was significantly
reduced (Figures 6B, 7A)
.
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| Discussion |
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This study provides the first evidence that pretreatment of rats with calpain inhibitor I attenuates 1) the development of carrageenan-induced pleurisy, 2) the infiltration of the lung with PMNs (histology and MPO activity), 3) the degree of lipid peroxidation in the lung, 4) the degree of lung injury (histology) caused by injection of carrageenan, 5) the development of collagen-induced arthritis, 6) the infiltration of joints with PMNs (histology), 7) the degree of plasma lipid peroxidation, and 8) the degree of joint injury (histology, radiography) in rats treated with type II collagen. All of these findings support the view that calpain inhibitor I attenuates the degree of acute and chronic inflammation in the rat.
What, then, is the mechanism by which calpain inhibitor I protects
joints against this inflammatory injury? Activation of the
transcription factor NF
B plays an important role in the expression
of iNOS.47-50
An enhanced formation of NO by iNOS may
contribute to the inflammatory process.39-42
This study
demonstrates that calpain inhibitor I attenuates the expression of iNOS
in the lung from carrageenan-treated rats (Figures 2, 3B)
and in joints
from collagen-treated rats (Figure 11B)
. Thus, the reduction of
the expression of iNOS by calpain inhibitor I may contribute to the
attenuation by this agent of nitrotyrosine in lungs from
carrageenan-treated rats (Figure 4B)
and in joints from
collagen-treated rats (Figure 10B)
. Nitrotyrosine formation,
along with its detection by immunostaining, was initially proposed as a
relatively specific marker for the detection of the endogenous
formation "footprint" of peroxynitrite.51
There is
recent evidence, however, that certain other reactions can also induce
tyrosine nitration; eg, the reaction of nitrite with hypochlorous acid
and the reaction of myeloperoxidase with hydrogen peroxide can lead to
the formation of nitrotyrosine.52
Increased nitrotyrosine
staining is considered, therefore, as an indication of "increased
nitrosative stress" rather than a specific marker of the generation
of peroxynitrite.
ROS and peroxynitrite produce cellular injury and necrosis via several
mechanisms, including peroxidation of membrane lipids, protein
denaturation, and DNA damage. ROS produce strand breaks in DNA, which
trigger energy-consuming DNA repair mechanisms and activate the nuclear
enzyme PARP, resulting in the depletion of its substrate NAD in
vitro and a reduction in the rate of glycolysis. As NAD functions
as a cofactor in glycolysis and the tricarboxylic acid cycle, NAD
depletion leads to a rapid fall in intracellular ATP. This process has
been termed "the PARP Suicide Hypothesis." There is recent evidence
that the activation of PARP may also play an important role in
inflammation.24,52-55
We demonstrate here that calpain
inhibitor I attenuates the increase in PARP activity in lungs from
carrageenan-treated rats (Figure 4D)
and in joints from
collagen-treated rats (Figure 10D)
.
The promoter region of the murine and human COX-2 genes contains
binding sites for NF
B.56,57
The expression of the COX-2
gene is activated by oxidant stress,58
and reactive oxygen
intermediates cause the activation of NF
B,59
suggesting
that NF
B is one of the transcription factors involved. The increase
in prostaglandin formation (COX activity) by murine osteoblasts (cell
line MC3T3-E1) involves the activation of NF
B.60
There is good evidence in this and in other models of inflammation that an enhanced formation of prostanoids after the induction of COX-2 contributes to the pathophysiology of local and chronic inflammation61,62 and that selective inhibitors of COX-2 exert potent anti-inflammatory effects.59-61 We demonstrate here that the increase in the levels of PGE2 caused by injection of carrageenan into the pleural cavity is reduced in the exudate of calpain inhibitor I-treated rats. The enhanced formation of PGE2 is secondary to the expression of COX-2 protein, as 1) there was no increase in the expression of COX-1 protein (detected by immunohistochemistry) after carrageenan injection and 2) selective inhibitors of COX-2 activity, including NS-398 (nimesulide) and SC-58125 (Celecoxib), markedly abolished the increase in PGE2 caused by the injection of carrageenan into the pleural space.64,65 Thus we propose that calpain inhibitor I reduced the expression of COX-2 protein and activity caused by injection of carrageenan into the lung and joints from collagen-treated rats.
Inhibition of calpain I activity reduces the injury associated with ischemia reperfusion of the brain,65-67 liver,68 and heart.69-72 The mechanism by which inhibitors of calpain activity protect tissues/organs against reperfusion injury is not entirely clear. Calpain acts on several substrates causing proteolytic modifications of proteins, which results in changes in their biochemical and morphological parameters, which are highly likely to be implicated in the pathological processes associated with ischemia reperfusion injury. Activation of calpain results in the proteolysis of several cellular proteins, mostly associated with the cellular membrane, including cytoskeletal proteins (eg, spectrin, fodrin, and microtubule-associated proteins), membrane proteins (eg, growth factor receptors, adhesion molecules, and ion transporters), enzymes (kinases, phosphatases and phospholipases), as well as cytokines and transcription factors (reviewed in ref 2 ). Although many of these may be implicated in mechanisms contributing to inflammation, the exact role of calpain activation in inflamed tissues has not been clearly defined. Thus in the present study we demonstrated for the first time that calpain inhibitor I reduced organ injury (lungs and joints) during inflammation.
In conclusion, this study demonstrates that the degree of acute and chronic inflammation is significantly attenuated in calpain inhibitor I-treated rats. The mechanisms of the anti-inflammatory effect of calpain inhibitor I are not entirely clear. It appears that calpain inhibitor I reduced the recruitment of neutrophils, the expression of iNOS and COX-2 protein and activity, and ultimately the degree of peroxynitrite formation and tissue injury. This effect of calpain inhibitor I is very likely secondary to the prevention by calpain inhibitor I of endothelial oxidant injury and, hence, to preservation of endothelial barrier function. These results support the view that the overproduction of reactive oxygen or nitrogen free radicals contributes to acute and chronic inflammation. Finally, we propose that calpain inhibitor I may be useful in the therapy of conditions associated with local or systemic inflammation.
| Acknowledgements |
|---|
| Footnotes |
|---|
Supported by a grant from the MURST 40%.
Accepted for publication August 3, 2000.
| References |
|---|
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B, on the circulatory failure and multiple organ dysfunction caused by endotoxin in the rat. Br J Pharmacol 1997, 121:695-704[Medline]
B-
is necessary for activation of transcription factor NF-
B. Nature 1993, 365:182-185[Medline]
B/Rel in induction of nitric oxide. J Biol Chem 1994, 269:4705-4708
, and lipopolysaccharide. J Clin Invest 1995, 95:1669-1675
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S. Cuzzocrea, E. Ayroldi, R. Di Paola, M. Agostini, E. Mazzon, S. Bruscoli, T. Genovese, S. Ronchetti, A. P. Caputi, and C. Riccardi Role of glucocorticoid-induced TNF receptor family gene (GITR) in collagen-induced arthritis FASEB J, August 1, 2005; 19(10): 1253 - 1265. [Abstract] [Full Text] [PDF] |
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A Ballinger, O Azooz, C Thiemermann, and S Cuzzocrea Calpain inhibitor I and colonic inflammation induced by DNBS in the rat Gut, March 1, 2002; 50(3): 440 - 441. [Full Text] [PDF] |
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